Crystal-like bundles in intrafibrillar amorphous regions and nonlinear viscoelasticity of oriented semicrystalline polymers

A phenomenological model of the viscoelasticity of highly oriented polymer systems is developed on the basis of the results of studying the relaxation of such systems (e. g., fibers of polyethylene terephthalate, polyamide-6, polyvinyl alcohol, and other polymers) in the loaded state. The effect of an applied load on their relaxation spectra agrees qualitatively with the deformation behavior of crystal-like bundles that are present in amorphous intercrystalline layers of the long period fibrillar supermolecular structure.